'Liam doesn't like me," shrugs his older brother. "He confuses love with hate. 'I love you.' No, Liam, I think you'll find you fucking hate me." Sitting in his management's central London HQ, Noel Gallagher recounts a recent disagreement. Oasis are about to release Stop the Clocks, their first retrospective. In the accompanying booklet, the lyrics for each of the 18 songs appear beside an image. The picture Noel chose to go next to Songbird - the only track written by Liam - was a red brick wall. "Because it's a love song about his bird," explains Noel. "And red is the colour of love."

But Liam, who wrote the song for his long-term partner, Nicole Appleton of All Saints, didn't take it that way. "I got a message on my answer machine," sighs Gallagher. "He was like, 'The colour red? Beside the song I wrote about my missus? Who I've got a child with? How fucking dare you!'" Gallagher tells the tale with a mixture of amusement, resignation and disbelief. "He only had to say he'd like to change it. No problem. But instead it descended into personal abuse." Liam's rant continued until the tape ran out. "I listened to it with my missus," says Noel. "She was going, 'You and your kid are actually insane. It's amazing you've managed to get this far.'"

But, somehow, here they still are. The Gallaghers may be Oasis's only original members, but their massive following remains. Last year's warmly received Don't Believe the Truth sold 2.5m copies, propelling Oasis on to a worldwide tour to 1.7 million people in 26 countries. They plan to record the follow-up in 2007. "The empire is still building," says Gallagher.

For now, though, the 39-year-old is looking back. On completing their six-album deal with Sony, Oasis were asked to release a greatest-hits collection.

Gallagher wasn't keen, but aware that Sony actually owns the band's songs, he agreed to support a best-of, featuring his selection of Oasis favourites.

It's a belting collection, with an intriguing tracklisting. Of the 18 songs, four are B-sides and four album tracks - meaning only 10 of Oasis's 22 top-40 hits feature. The rejects include Roll With It, Oasis's contribution to the famous 1995 chart battle with Blur. "I don't like that song," admits Gallagher, who seems comfortable enough with his achievements - and himself - to be self-critical. But the most telling statistic is that 14 of the 18 tracks were released in 1994 or 1995. In other words, Gallagher seems to be admitting what many of us believed: that his band - and his songs - peaked over a decade ago.

"Yeah, of course," he shrugs. "We're talking about the best of Oasis here. If you stop the man in the street and ask 'What's Oasis's best album?', a few might say Don't Believe the Truth, which is great, but the squares will say Morning Glory and the cool people will say Definitely Maybe. That album should just be called the Best of Oasis." He leans forward. "Look. I was a superhero in the 90s. I said so at the time. McCartney, Weller, Townsend, Richards, my first album's better than all their first albums. Even they'd admit that."

So why didn't he remain a superhero into the next decade? "Because those songs were written in my 20s. All I had in the world was a guitar and a Dictaphone. When you're young, you write about being young and shagging and drugs and drinking. You can't do that when you're 39. I was a different person then."

These days, Gallagher's Saturday nights involve watching Match of the Day, and he hasn't touched cocaine since 1998.

"Cocaine itself isn't that bad," he says. "It just makes you drink more and that's the worst drug there is. Especially when you're surrounded by people whose psychosis sets in the more they drink. But people think I stood up at a party and announced, 'That was my last line of cocaine, from this day forth I shall take no more,' and everybody sighed and left. It wasn't like that. The reason I packed it in was that it was only meant to be a weekend, which became a week, which became a month and so on. I just decided I couldn't be arsed any more."

Although Gallagher says his songwriting passion was reignited by Don't Believe the Truth, his inescapable problem is that any new Oasis album must compete with their first two records. "Which is completely unfair. If I knew how to write another Definitely Maybe, I'd do one every year. It astounds me that I wrote those songs. But nobody has ever bettered Definitely Maybe, don't pin it on my shoulders. The Arctic Monkeys came close, but that's it. They've got the tunes and the attitude. If only they could front it out."

At times this year, the Arctic Monkeys have seemed almost embarrassed by their success. It's the antithesis of the Oasis way. "I've never understood that kind of thing. Like the Clash going, 'We're not playing on telly.' Well fuck off then. When we first started we said we were the greatest band in the world. We should have said we were the best band in the charts. 'Cos to me, the world is the charts. I don't give a fuck about Radiohead and all that indie nonsense. I was brought up on the top 10. Slade, T.Rex, David Bowie. If you're not in the charts, you don't exist. BMX Bandits? Four people are listening to it in Hull. I went in there to get Phil Collins' severed head in my fridge by the end of the decade."

Which, in a manner of speaking, he did. "I came from a shithole in Manchester, right, so it was all brilliant to me. Even touring in a transit van was better than being in my flat. Then when we got a deal, we were like: 'Bring it on!' I wanted the big hairdo, big shades, big car, big house, swimming pool, jet, drug habit, a mirrored top hat and a chimp. All of it. The Kasabian lads told me they'd only get out of bed to read about us in the paper. And what would you rather read? 'The guy from Keane's been to a rabbit sanctuary 'cos one of the rabbits needed a kidney implant, so he swapped his with it' - or 'Liam Gallagher sets fire to a policeman in cocaine madness, while his brother Noel runs down Oxford Street nude'?"

No doubt Kasabian loved the story about Gallagher visiting the victorious Tony Blair, in 1997, at his Downing Street reception and asking the new PM how he'd managed to stay up all night during the election; "Probably not by the same means you did," was Blair's knowing reply.

Having effectively been New Labour's house band, what does Gallagher think of Blair now? "Well, I think that Britain is a better place than it was before the Labour party took over. Personally, I'd have loved Neil Kinnock to get in. He was gonna rip Margaret Thatcher's head off and shit down her neck. Then Tony Blair came along and it was like: 'Ah, he's gonna outsmart all of these public schoolboy cunts.' But we all got carried away in 97. Once the veneer wore off - even taking the Iraq debacle out of the equation - we've all just given a massive shrug. I think the Labour party's crowning achievement is the death of politics. There's nothing left to vote for."

Gallagher is concerned David Cameron will win the next election, "although even if he does, it won't matter because it won't change anything. He's just saying the same as Tony Blair was saying. Gordon Brown over David Cameron? When I see them on television, I switch them both off."

Gallagher, though, is contented. He has no sympathy for those for whom fame is a burden. He doesn't sit in his country house (though he has one) counting his millions (though he has several). "Life is a great thing, why shut yourself away from it? I can't understand people like Elton John and Robbie Williams going straight from their blacked-out limos to a restaurant. I stand in the queue at Waitrose. More rock stars should do that. Forget therapy, go to the supermarket and interact. The staff in my local Waitrose are really blase about me now. They'll be like, 'Him? Oh he's in here all the fucking time. And between me and you, he doesn't eat very well.'"

Ten years ago, Gallagher's life was almost entirely focused on Oasis. But even though he says its not his sole passion any more, that he has a full life outside Oasis, he insists he is still very much the band's leader. "If I said the next album was going to be Irish reggae, then it would be." Nevertheless, he's relinquished control to the point where all four members contribute songs, something he admits would have been unthinkable in the mid-1990s. "I've got to say a lot of weight was lifted from my shoulders when Liam, Andy and Gem started to deliver songs for Don't Believe the Truth and they were actually good."

Gallagher readily concedes his brother's earliest songs weren't great. "But you either say, 'That's shit, fuck off,' and he retreats into his shell. Or you go, 'Look, I'm not into it, but if you believe in it, it goes on - but you're taking the flak for it.' Liam used to say in interviews, 'Noel won't let me write.' But back in the 1990s while I was grafting, he was shooting Stella into his arms 'cos he thought it would mainline into his brain quicker. So I was like, 'Well write one, and we'll take it from there.' I'm glad he's done it, because the great ones are great and the shit ones he gets slagged off for. And there's nothing I like more than reading people slagging Liam off." Gallagher cackles.

"The reason he doesn't like me is that I'm indifferent to him," he explains. "I can come off tour, put the bags down and shut the door. Liam can't do that. He wants to carry on. Plus, he insults me and I don't like being around people who insult me."

The brothers don't exchange Christmas or birthday presents and have only seen each other "two or three times" since returning from tour in March. "I just don't need to be in the gang all the time," says Gallagher.

Presumably he has considered the possibility that Liam's insults stem from jealousy; after all, Noel's the older, brighter one, the one who wrote 17 of 18 songs on Stop the Clocks, the one people respect more. "But he's got nothing to be jealous of. Thing is, you say about the 17 songs, but Oasis is dependent on three equal parts. That's him, me and the songs. It's all about that struggle and it wouldn't be Oasis without him. But Liam can't see that. 'Cos when he has a drink, he's got an enemy complex. And a serious inferiority complex. But, y'know, he is my brother. And although I don't like him, I do love him to bits."

Perhaps, I suggest, you should buy him a Christmas present this year. "Yeah, maybe I will," nods Noel, thoughtfully. "I'll get him a fucking straitjacket."

· Oasis's Stop the Clocks EP is released on Monday on Sony. The Stop the Clocks 2CD album is released on November 20.